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Vadlamudi Brahmananda Rao
and
Valdo Da Silva Marques

Abstract

Water vapor characteristics over northeast Brazil for two contrasting years are discussed. During the wet year 1974, the precipitation efficiencies were less than 20% over the interior dry region and during the dry year 1976, they were reduced to 10% or less. The reduction is mainly due to low precipitation in 1976. Calculation of water vapor flux showed that in both wet and dry years, the flux is inward in the east sector and outward in the west sector. This suggests the importance of the South Atlantic Ocean in providing water vapor for NE Brazil. During the wet year, the lower tropospheric flow is convergent and in the northwest part, the direction of flow is more northerly/less southerly. During the dry year the opposite occurred. This indicates the possible role of the Intertropical Convergence Zone in the interannual variations of climate over NE Brazil.

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Jennifer M. Collins
,
Rosane Rodrigues Chaves
, and
Valdo da Silva Marques

Abstract

The variation of air temperature at 2 m above the earth’s surface in South America (SA) between 1948 and 2007 is investigated primarily using the NCEP–NCAR reanalysis. In December–February (austral summer), the majority of SA has a mean temperature between 21° and 24°C during 1948–75, and for 1976–2007 the mean temperature is above 24°C. In June–August (austral winter), warmer temperatures are observed in the tropical region in the recent period. The results indicate that Northeast Brazil (NEB) and central Brazil are warmer in the more recent period. In the last seven years (2001–07) compared to the earlier periods, greater warming is noted in the tropical SA region, mainly in NEB and over the North Atlantic Ocean, and cooling is observed in part of the subtropical SA region. Supporting evidence for the warming in Brazil is given through analyses of station data and observational data. The results presented here indicate that the climate change over SA is likely not predominantly a result of variations in El Niño–Southern Oscillation (the most important coupled ocean–atmosphere phenomenon to produce climate variability over SA). Instead, the climate changes likely occur as a response to other natural variability of the climate and/or may be a result of human activity. However, even without ascertaining the specific causes, the most important finding in this work is to demonstrate that a change in the temperature patterns of SA occurred between 1948 and 2007.

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